The prevalence of obesity among adults is stabilizing after decades of unrelenting increases and about 68% of Veterans are considered either overweight or obese. Obesity is the second leading cause of preventable deaths in the US and is associated with a wide range of diseases, such as hypertension, type 2 diabetes mellitus, coronary heart disease, and osteoarthritis. These clinical risks lead obese patients to incur disproportionately high health expenditures. In 2008, annual health expenditures attributable to obesity were estimated to be $147 billion, concentrated among morbidly obese patients. In 2013, 28.2% of overall health expenditures for adults was incurred for obesity-associated care. Currently, three types of weight management interventions are available to overweight and obese VA patients: behavioral lifestyle counseling, pharmacotherapy and bariatric surgery. The most widely used of these interventions is behavioral counseling through the MOVE! program. Despite the widespread adoption of MOVE! as a first line treatment for obesity in VA, MOVE! participation has been associated with modest short- term weight loss and evidence is absent regarding the clinical and economic effectiveness of MOVE! beyond a 12-month follow-up. No prior VA studies have examined the natural history of weight gain, long-term expenditures of normal weight, overweight and obese Veterans, or changes in weight and expenditures attributable to MOVE!. It is important to understand longitudinal (20-year) patterns of VA healthcare expenditures by BMI progression to characterize the long-run scope of the problem of obesity in VA. Such results will then provide significant context for evaluating the health and economic effectiveness of MOVE! participation. Taken together, the four specific aims will enable an examination of impact of MOVE! on Veteran outcomes in the context of VA's overall population-level weight management strategy on eligible Veterans: Aim 1: Identify latent classes of different BMI progression trajectories between 2000-2019. Aim 2: Estimate differences in long term VA expenditures between latent BMI classes. Aim 3: Identify the average treatment effect of MOVE! and characteristics of Veterans who experience the greatest weight reductions following MOVE! participation. Aim 4: Identify the average treatment effect of MOVE! on expenditures and characteristics of Veterans who experience the greatest reduction in VA expenditures following MOVE! participation. Next Steps: The examination of 20-year expenditures associated with obesity and differential effects of MOVE! responds to one of the top four strategic goals identified in the VA FY 2018-2024 Strategic Plan by informing approaches to focus resources more efficiently. This study also addresses HSR&D's cross-cutting priority of business case and policy analysis and the Healthcare Informatics priority through the analysis, validation, and application of Big Data sources to improve individual and population health. This research will also enable us to formalize an algorithm to identify patients most likely to benefit from MOVE!, as well as those unlikely to achieve significant clinical weight loss through MOVE!. Following identification of Veterans at greatest risk for obesity and high VA expenditures, and of Veterans who experience the greatest weight and expenditure improvements following weight loss intervention, we will partner with NCP to determine how best to implement a prioritization strategy to develop need-tailored behavioral programs.